Handle `notification_id` query param gracefully for user show

There is no need to block users from viewing a user when
someone is sharing a link from his notifications with the
`notification_id` attached as a query param. The `notification_id`
query param is used to render the notification toolbar for an
authorized users. If someone without authorization is using the
same link, we should simply not render the toolbar, but still show
the user show view.